As the year 1968 unfolds, John "Chickie" Donohue, a former Marine Corps veteran turned merchant seaman, finds himself ensnared in a cycle of stagnation, living with his family in Inwood, New York City. His sister, Christine, remains steadfast in her vehement opposition to the Vietnam War, constantly reminding him of the dire consequences of such conflicts. The atmosphere takes a somber turn during a gathering for the funeral of an old friend, Johnny, when they receive the heartbreaking news that another buddy, Tommy, is missing in action. This revelation casts a shadow over the group, pushing Chickie and his friend Red to brainstorm ways to uplift their spirits amidst the sorrow.
In the midst of this melancholy environment, Chickie devises an audacious plan: he decides to travel to South Vietnam, equipped solely with a duffle bag stuffed with Pabst Blue Ribbon beer cans. He signs up to a ship bound for Saigon, where he meets Tommy Collins, a no-nonsense military police officer who is initially skeptical of Chickie's rather reckless endeavor.
As they navigate the perilous landscape, Chickie and Collins collaborate on a scheme to connect with their fellow servicemen, all while Collins cautions him about the risks involved. They receive assistance from Hieu, a local with valuable knowledge of the area. Their first stop is the esteemed Caravelle Hotel, where Chickie encounters both American and British reporters who resonate with his anti-war views.
Chickie's subsequent move involves hitching a ride on a military caravan headed to Bien Hoa Air Base, from where he's airlifted to Danang Air Base and eventually lands at LZ Jane with the goal of finding Rick Duggan, a soldier serving in the 1st Cavalry Division. When Chickie finally connects with Duggan, he quickly realizes the chaos as enemy fire erupts around them, forcing him to seek cover.
As night descends, Chickie distributes his beloved beers once again, giving everyone a brief respite from the surrounding turmoil. In this fleeting moment of calm, Duggan bears tragic news about their friend Reynolds, who has sadly lost his life. After bidding farewell to Duggan, Chickie finds himself aboard a helicopter heading towards uncertainty, in the company of two CIA agents who mercilessly interrogate and eliminate a helpless prisoner.
As the helicopter whisks him away from danger, Chickie ponders over the chaotic adventure that began since his arrival at Kontum Airfield. Initially, he looks for a lift to Saigon; however, one officer's suggestion to accompany him to Pleiku Air Base fills him with dread as he spots an ambush ahead. While evading capture, he dives into the jungle, eluding his pursuers until they retreat. That evening, an old acquaintance, Kevin "Looney" McLoone, serendipitously finds Chickie and, after some convincing, agrees to take him to Pleiku. Grateful, Chickie tosses a beer to McLoone as the helicopter ascends into the night sky.
Meanwhile, back in Saigon, Chickie discovers that his ship has left earlier than expected due to alarms of an incoming attack and is now bound for the Philippines. Hieu guides Chickie to the U.S. Embassy, where a kind stranger assists him in booking a flight to Manila to reunite with his crew. Returning to the Caravelle Hotel, Chickie shares compelling photographs with journalists as evidence of his excursion to LZ Jane. Just as he is about to catch his breath, chaos strikes as the Viet Cong launches a surprise Tet Offensive on Saigon, taking everyone by surprise. Amidst the turmoil, Chickie and Arthur Coates head into the fray, where Chickie tragically witnesses the senseless killing of Hieu during the devastating assault on the U.S. Embassy.
The next morning, Coates captures the eerie silence and destruction following the embassy's bombing, with a colossal explosion visible in the distance. As they approach the scene, Coates reveals that the military prefers to fabricate a breach in the embassy wall rather than concede that the attack was an inside job. At Long Binh Post, Chickie takes a moment to share a drink with his last wounded comrade, Bobby Pappas, who confirms the devastating news of Tommy Minogue's death.
When Chickie returns home, his understanding of the war is irrevocably transformed. In a poignant scene, he finds himself amidst tributes to fallen soldiers in the park, sharing his final beer with Christine. The film concludes with a flash-forward reveal, showing that Collins, Duggan, McLoone, and Pappas all survived the war and made it back home, while Chickie's own life progressed into a lengthy career with the New York City sandhoggers union. A modern photograph of the group enjoying drinks serves as a moving epilogue, symbolizing the lasting bonds formed amidst the ravages of conflict.
